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Gravitational Wave Astronomy
using 0.1Hz space laser
interferometer
Takashi Nakamura
GWDAW-8 Milwaukee
2003/12/17
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In 2001 we considered what we
can do using 0.1 hertz laser
interferometer ( Seto, Kawamura
and TN : PRL 87 221103)
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Motivation to DECIGO
comes from extra solar planets
• Many extra solar planets are found using many
absorption lines (～5000) of nearby G type stars
since small orbital motion up to 10m/s can be measured
• Loeb (1998) proposed to apply this techniques to many
QSO absorption lines so that two observations between
ten years yield direct measurement of Cosmic
Acceleration and thus dark energy
Our point is
• Use gravitational waves from coalescing binary neutron
stars at z=1 instead of QSO absorption lines
• Then the frequency of GW (a year to ten years before
the coalescence) should be 0.1 Hz band where little
proposal for detectors existed
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Our Point and Strategy
• Consider the ultimate
possible detector in the
sprit of
• necessity is the mother of
the invention
• We call the detector
DECIGO( DECi hertz laser
Interferometer Gravitational
wave Observatory)
• We may not see the
construction of DECIGO in
our life since highly
advanced technology is
needed , we are sure that
our children or grand
children will decide and go
DECIGO.
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Equation of state of the universe
• Even if
is known accurately as a function of z, for
example by SNAP, the density and the pressure are not
uniquely determined. (Weinberg 1970; Chiba and TN
1999)
• The value of
should be determined by other
observations.
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Matched Filter Analysis Using
Ultimate DECIGO
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• After subtracting these binaries and possible other
sources from the row data, we might observe
• the primordial gw background even if
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Punch Point of Ultimate DECIGO
a)
100,000 Mass of neutron stars, Black Hole will give us
mass function of NS and BH
b) Direct measurement of Acceleration of the universe;
Independent measurement of the curvature of the
universe, independent information of EOS of the
universe
c) Background gw predicted by inflation model
up to
Completely independent information from MAP and
PLANCK
d) If the fundamental scale is Tev, then the redshifted GW
at T=Tev is just 0.1Hz Band. We may see something.
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Other Sources are also important
a) Formation of Intermediate mass BH (IMBH)
b) Coalescence of IMBH binary
c) Compact star falling into IMBH
d) GRB Jets
e) White dwarf binary
f) Oscillation of WD
g) WD+NS(BH) binary
h)………….
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Various version of DECIGO is
possible
A) the same spec as LISA with 0.01 arm
length 1w laser, low acceleration noise
B) The ultimate one
quantum limit;100kg mirror, 10MＷ laser
C) The practical one
300w laser; 3m mirror…… similar to
BBO (Big Bang Observer)
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If we use the same spec as LISA
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Spec of Practical DECIGO
• 300w laser, 3m mirror, 0.01 LISA acceleration
noise………..similar to BBO(Big Bang Observer)
• POINT is
• Practical DECIGO and ground based interferometer and bars
can observe the same source at different frequency and time .
• Here we like to point out
• Deci Hertz laser interferometer can determine the position of
the coalescing binary neutron stars within an arc minute a week
before the final event to black hole (Takahashi and TN (2003 )
ApJ 596 L231)
• New binary pulsar suggests the nearest distance is ～50Ｍｐｃ
comparable to the nearest GRB980425(40Mpc)
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Accuracy can be ～10arcsec
Practical DECIGO or BBO
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Angular Resolution
• In any astronomy including
Gamma Ray Astronomy and Gravitational
Wave Astronomy
Angular resolution is crucial
Good example is Gamma Ray Bursts
1973-1997 Distance was not determined.
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１９９７ Beppo-SAX satellite
• Afterglow of GRB in X-ray
• X-ray telescope with arc
minute accuracy
• X-ray counter Part
• Optical telescope
• OT (Optical Transient)
• Optical Afterglow
• HOST Galaxy
• Spectrum
• Cosmological redshift
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Cosmological GRB！！
• Z>0.835 for
GRB970508
•
•
GRB
z=0.768 0.835
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Optical Afterglow and Host Galaxy
•
•
GRB ９７０２２８
GRB ９９０１２３
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Distance to short GRBs is not known
• short GRB might be coalescing binary
neutron star
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Angular Resolution in Gravitational
Wave Astronomy
• Essentially time of flight method
•
•
• For periodic or chirp signal
• LIGO and LISA
for S/N～100
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How to determine the direction
• Time of Flight Method
GW
detector １
detector ２
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Practical DECIGO
is expected for S/N=100
• Consider 1.4 solar mass binary neutron
star at 300Mpc
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• We consider NS binary (1.4
)and BH binary
(10-1000)
at 300Mpc for 1yr and 10yr
observation
• The errors scale as
for the
change of the distance and the orientation of the
binary
• The accuracy of the chirp mass and the reduced
mass are
for 1.4
NS binary, respectively
The distance to the binary is determined by
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Point All the Detectors to
coalescing binary
neutron star (black hole) event !!
• The direction as well as the time of the
event are known beforehand
• All band electromagnetic detectors from
radio to ultrahigh energy gamma rays
• Possible neutrino detectors
• Tune the high frequency gravitational
wave detectors to catch ISCO, QNM and
so on
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• Recent discovery of new
binary pulsar
PSR J0737-3039
• Coalescence rate
180/Myr/Galaxy
• The nearest event in a
year is 50Mpc
• S/N increases by a
factor 6
• Then the position
accuracy becomes
10arcsec and 0.01sec
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Conclusion
• DECIGO/BBO can obtain
• 100,000 mass of neutron stars and black holes
• Direct measurement of the acceleration of the
universe
• Background gravitational waves
• Other sources such as IMBH…….
• The angular position and the time of the
coalescence a week before with 10arcsec and
0.01 sec accuracy
• Point all possible detectors to the source and
Possible identification of short duration GRB
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